As is known in the art, packaging films which incorporate a seal area having a peelable/resealable film interface provide for the consumer an easy means to both open a container without having to tear the package and re-close the container as often as needed. In general, peelable/resealable film interfaces are formed when two film surfaces are bonded or sealed together during the package fabrication process. This seal area or bond is considered “peelable” if the consumer simply grasps a portion of the film and pulls or “peels” it away from a second portion-thereby causing at least two adjacent film layers to delaminate and exposing the surface of each layer. The initial force needed to separate the layers is relatively strong before the package is opened in order for the seal area to withstand the expected abuse during the packaging operation, distribution, and storage. By contrast, after the package has been initially opened, the peeling force required to break the seal and re-open the package is relatively weak thereafter. Moreover, the bond is considered “resealable” if the consumer simply engages the two exposed film surfaces together-thereby causing the seal between the layers to re-establish. Generally, the force require to “reseal” the two exposed surfaces is proportional to the pressure exerted on the seal area or bond by the consumer. The means of forming peelable/resealable bonds and their use in packaging applications are disclosed in the art.
U.S. Pat. No. 6,777,050 to Engelaere describes a cover for food containers which comprises a support layer, a pressure-sensitive adhesive layer, and a tearable-heat sealable layer. The tearable-heat sealable layer is fabricated from polyethylene or metallocene catalyzed polyethylene and the pressure-sensitive adhesive layer is formed from polyurethane.
U.S. Pat. No. 5,089,320 to Straus et al. discloses a packaging material containing a substrate layer of polyethylene terephthalate or high density polyethylene, an adhesive layer comprising a tacky adhesive, and a heat seal layer of polystyrene, polyvinylidene chloride, or ionomer. Delamination of packaging material may occur either between the substrate or adhesive layers or the adhesive and heat seal layers.
U.S. Pat. No. 4,786,190 to Van Erden et al. discloses a bag having a pressure-sensitive adhesive strip secured to the inside surface of a flap which is covers the mouth of the bag. When the flap is folded over the mouth onto the bag, it may be peelably secured to an outside surface of the bag.
U.S. Pat. No. 4,673,601 to Lamping et al. describes a film for sealing a container comprising a carrier layer of polyester, polyamide, polyvinyl chloride, biaxially oriented polypropylene, regenerated cellulose, aluminum, or paper, an adhesive layer of ethylene/vinyl acetate copolymer, styrene/butadiene/styrene block copolymer, styrene/isoprene/styrene block copolymer, or polyacrylate, and a covering layer of polyethylene, polypropylene, polyamide, polyvinyl chloride, hot melts, regenerated cellulose, aluminum, or paper. The film will delaminate at the cover layer/adhesive layer interface.
U.S. Pat. No. 3,454,210 to Spiegel et al. discloses a cover film for packaging containers having a layer of polyethylene, a layer of pressure-sensitive adhesive, and a rupturable layer of polyethylene.
U.S. Pat. No. 3,329,331 to Morgan describes a laminate for manufacturing resealable containers. The laminate comprises a paper base material, a lacquer coating on the base material, a pressure-sensitive adhesive, and a surface sheet of either paper or plastic. The pressure-sensitive adhesive is releasably and resealably adhered to the lacquer coating on the base material.
There still remains a need in the packaging industry for a peelable/resealable film having improved functionality. Such a film would provide a peelable/resealable bond or inter-layer interface which would allow the consumer to easily open and re-seal a package formed from this film as often as desired. Ideally, such a film would allow the a peelable/resealable bond to open at an initial predetermined peel force and re-open at a second and different predetermined peel force. The present invention provides such a peelable/resealable film.